This study was shortlisted for the 2023 Thesis of the Year Award and completed as part of Caitlin Duggan's BSc (Hons) in Veterinary Bioscience, which she studied at Aberystwyth University.

Take home message: Bovine tuberculosis (bTB) cases are predicted to decrease in cattle across England and Wales with an R0 of less than 1 shown in this study. Farmers in high bTB risk areas should consider the number of cattle they house in their holdings.  A higher cattle density was linked to more bTB cases therefore providing a potential solution to reduce bTB in herds. In summary, while bTB cases are expected to decrease, complete eradication by 2038 remains challenging due to the observed trends and control strategies. Further research on new control strategies being introduced in 2025 to predict their impact will be crucial.

Will bovine tuberculosis (bTB), be eradicated by 2038 as the government plan? Current control measures include the topical culling of badgers adopted by England whereas Wales uses badger trapping and testing to only cull those that turn out positive for bTB. Previous studies have used modelling for bTB to predict the number of cattle infected with bTB at certain time points. This study specifically focuses on both England and Wales, which is unique compared to previous research.

The study aimed to find the R0 which represents how many new cases one infected individual can cause in a group of susceptible cattle. If R0 is greater than 1, the disease spreads easily. Also, the study aimed to define how long it takes for cattle exposed to become infected with bTB as currently estimates vary from months to years. The research used mathematical models based on data collected by the Animal and Plant Health Agency (APHA) between 2016 and 2021. The model took into account the number of cattle and the average birth rate, death rate, sensitivity to skin testing, rate of transmission, and rate of progression from exposed to infected.

The results showed cattle exposed to bTB were predicted to become infected after approximately 508 days falling between the previously established range. Managing this long incubation period poses a challenge for disease control efforts. The study predicted an R0 of 0.95, similar to previous reports, and indicates that cases of bTB are decreasing in England and Wales. This suggests that control strategies have been effective in reducing bTB. However, this value might underestimate the transmission risk due to wildlife (e.g., badgers) not being included in the model. Interestingly, the study found a link between the number of cattle within an area and the R0. Regions in the West of England with higher cattle numbers had a higher R0 compared to the East of England. Reducing cattle density in high-risk areas could help control bTB prevalence. Current control strategies are showing a positive effect in reducing cases of bTB in England and Wales. The findings suggest both countries will not be bTB-free by 2038 without further control strategies being implemented to reduce the R0.

Dr Issy Lewis, Animal Health Lecturer, Hartpury University.